Evaluation

1. history is critically important. Check for exposure to drugs that affect pupillary size, trauma. Look
at old photos (e.g. driver’s license) for physiologic anisocoria

2. Pupillary exam

3. a non-contrast CT is usually not helpful and can provide a false sense of security.

Differential diagnosis

1. physiologic anisocoria: occurs in ≈ 20% of population (more common in people with a light iris).
Familial and nonfamilial varieties exist. The difference in pupils is usually <0.4 mm. The inequal-
ity is the same in a light and dark room (or slightly worse in the dark)

2. pharmacologic pupil: the most common cause of sudden onset of anisocoria